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<pre><a name="line-1"></a><span class='hs-comment'>{-# LANGUAGE PatternGuards #-}</span>
<a name="line-2"></a><span class='hs-comment'>{-
<a name="line-3"></a> Reduce the number of import declarations.
<a name="line-4"></a> Two import declarations can be combined if:
<a name="line-5"></a> (note, A[] is A with whatever import list, or none)
<a name="line-6"></a>
<a name="line-7"></a> import A[]; import A[] = import A[]
<a name="line-8"></a> import A(B); import A(C) = import A(B,C)
<a name="line-9"></a> import A; import A(C) = import A
<a name="line-10"></a> import A; import A hiding (C) = import A
<a name="line-11"></a> import A[]; import A[] as Y = import A[] as Y
<a name="line-12"></a>
<a name="line-13"></a><TEST>
<a name="line-14"></a>import A; import A -- import A
<a name="line-15"></a>import A; import A; import A -- import A
<a name="line-16"></a>import A(Foo) ; import A -- import A
<a name="line-17"></a>import A(Bar(..)); import {-# SOURCE #-} A
<a name="line-18"></a>import A; import B
<a name="line-19"></a>import A(B) ; import A(C) -- import A(B,C)
<a name="line-20"></a>import A; import A hiding (C) -- import A
<a name="line-21"></a>import A; import A as Y -- import A as Y
<a name="line-22"></a>import A; import qualified A as Y
<a name="line-23"></a>import A as B; import A as C
<a name="line-24"></a>import A; import B; import A -- import A
<a name="line-25"></a>import qualified A; import A
<a name="line-26"></a>import B; import A; import A -- import A
<a name="line-27"></a>import A hiding(Foo); import A hiding(Bar)
<a name="line-28"></a>import List -- import Data.List
<a name="line-29"></a>import IO(foo) -- import System.IO(foo)
<a name="line-30"></a></TEST>
<a name="line-31"></a>-}</span>
<a name="line-32"></a>
<a name="line-33"></a>
<a name="line-34"></a><span class='hs-keyword'>module</span> <span class='hs-conid'>Hint</span><span class='hs-varop'>.</span><span class='hs-conid'>Import</span> <span class='hs-keyword'>where</span>
<a name="line-35"></a>
<a name="line-36"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Hint</span><span class='hs-varop'>.</span><span class='hs-conid'>Type</span>
<a name="line-37"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Util</span>
<a name="line-38"></a><span class='hs-keyword'>import</span> <span class='hs-conid'>Data</span><span class='hs-varop'>.</span><span class='hs-conid'>Maybe</span>
<a name="line-39"></a>
<a name="line-40"></a>
<a name="line-41"></a><a name="importHint"></a><span class='hs-definition'>importHint</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ModuHint</span>
<a name="line-42"></a><span class='hs-definition'>importHint</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>concatMap</span> <span class='hs-layout'>(</span><span class='hs-varid'>wrap</span> <span class='hs-varop'>.</span> <span class='hs-varid'>snd</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>groupSortFst</span>
<a name="line-43"></a> <span class='hs-keyglyph'>[</span><span class='hs-layout'>(</span><span class='hs-layout'>(</span><span class='hs-varid'>fromNamed</span> <span class='hs-varop'>$</span> <span class='hs-varid'>importModule</span> <span class='hs-varid'>i</span><span class='hs-layout'>,</span><span class='hs-varid'>importPkg</span> <span class='hs-varid'>i</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span><span class='hs-varid'>i</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>i</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>universeBi</span> <span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-varid'>not</span> <span class='hs-varop'>$</span> <span class='hs-varid'>importSrc</span> <span class='hs-varid'>i</span><span class='hs-keyglyph'>]</span><span class='hs-layout'>)</span> <span class='hs-varop'>++</span>
<a name="line-44"></a> <span class='hs-varid'>concatMap</span> <span class='hs-varid'>hierarchy</span> <span class='hs-layout'>(</span><span class='hs-varid'>universeBi</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-45"></a>
<a name="line-46"></a>
<a name="line-47"></a><a name="wrap"></a><span class='hs-definition'>wrap</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Idea</span><span class='hs-keyglyph'>]</span>
<a name="line-48"></a><span class='hs-definition'>wrap</span> <span class='hs-varid'>o</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyglyph'>[</span> <span class='hs-varid'>rawIdea</span> <span class='hs-conid'>Error</span> <span class='hs-str'>"Use fewer imports"</span> <span class='hs-layout'>(</span><span class='hs-varid'>toSrcLoc</span> <span class='hs-varop'>$</span> <span class='hs-varid'>ann</span> <span class='hs-varop'>$</span> <span class='hs-varid'>head</span> <span class='hs-varid'>o</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>o</span><span class='hs-layout'>)</span> <span class='hs-layout'>(</span><span class='hs-varid'>f</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span>
<a name="line-49"></a> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>x</span> <span class='hs-keyglyph'><-</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>simplify</span> <span class='hs-varid'>o</span><span class='hs-keyglyph'>]</span><span class='hs-keyglyph'>]</span>
<a name="line-50"></a> <span class='hs-keyword'>where</span> <span class='hs-varid'>f</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>unlines</span> <span class='hs-varop'>.</span> <span class='hs-varid'>map</span> <span class='hs-varid'>prettyPrint</span>
<a name="line-51"></a>
<a name="line-52"></a>
<a name="line-53"></a><a name="simplify"></a><span class='hs-definition'>simplify</span> <span class='hs-keyglyph'>::</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span><span class='hs-keyglyph'>]</span>
<a name="line-54"></a><span class='hs-definition'>simplify</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-55"></a><span class='hs-definition'>simplify</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>simplifyHead</span> <span class='hs-varid'>x</span> <span class='hs-varid'>xs</span> <span class='hs-keyword'>of</span>
<a name="line-56"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-varid'>x</span><span class='hs-conop'>:</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-varid'>simplify</span> <span class='hs-varid'>xs</span>
<a name="line-57"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>xs</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-varid'>fromMaybe</span> <span class='hs-varid'>xs</span> <span class='hs-varop'>$</span> <span class='hs-varid'>simplify</span> <span class='hs-varid'>xs</span>
<a name="line-58"></a>
<a name="line-59"></a>
<a name="line-60"></a><a name="simplifyHead"></a><span class='hs-definition'>simplifyHead</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span><span class='hs-keyglyph'>]</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span><span class='hs-keyglyph'>]</span>
<a name="line-61"></a><span class='hs-definition'>simplifyHead</span> <span class='hs-varid'>x</span> <span class='hs-conid'>[]</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-62"></a><span class='hs-definition'>simplifyHead</span> <span class='hs-varid'>x</span> <span class='hs-layout'>(</span><span class='hs-varid'>y</span><span class='hs-conop'>:</span><span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>case</span> <span class='hs-varid'>reduce</span> <span class='hs-varid'>x</span> <span class='hs-varid'>y</span> <span class='hs-keyword'>of</span>
<a name="line-63"></a> <span class='hs-conid'>Nothing</span> <span class='hs-keyglyph'>-></span> <span class='hs-varid'>fmap</span> <span class='hs-layout'>(</span><span class='hs-varid'>y</span><span class='hs-conop'>:</span><span class='hs-layout'>)</span> <span class='hs-varop'>$</span> <span class='hs-varid'>simplifyHead</span> <span class='hs-varid'>x</span> <span class='hs-varid'>ys</span>
<a name="line-64"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>xy</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-varid'>xy</span> <span class='hs-conop'>:</span> <span class='hs-varid'>ys</span>
<a name="line-65"></a>
<a name="line-66"></a>
<a name="line-67"></a><span class='hs-comment'>-- Useful fields in import are:</span>
<a name="line-68"></a><span class='hs-comment'>-- importModule :: ModuleName [same]</span>
<a name="line-69"></a><span class='hs-comment'>-- importPkg :: Maybe String [same]</span>
<a name="line-70"></a><span class='hs-comment'>-- importQualified :: Bool</span>
<a name="line-71"></a><span class='hs-comment'>-- importSrc :: Bool [False]</span>
<a name="line-72"></a><span class='hs-comment'>-- importAs :: Maybe ModuleName</span>
<a name="line-73"></a><span class='hs-comment'>-- importSpecs :: Maybe (Bool, [ImportSpec])</span>
<a name="line-74"></a>
<a name="line-75"></a><a name="reduce"></a><span class='hs-definition'>reduce</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span> <span class='hs-keyglyph'>-></span> <span class='hs-conid'>Maybe</span> <span class='hs-layout'>(</span><span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span><span class='hs-layout'>)</span>
<a name="line-76"></a><span class='hs-definition'>reduce</span> <span class='hs-varid'>x</span> <span class='hs-varid'>y</span> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>qual</span><span class='hs-layout'>,</span> <span class='hs-keyword'>as</span><span class='hs-layout'>,</span> <span class='hs-varid'>specs</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>x</span>
<a name="line-77"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>qual</span><span class='hs-layout'>,</span> <span class='hs-keyword'>as</span><span class='hs-layout'>,</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>ImportSpecList</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>False</span> <span class='hs-varid'>xs</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>importSpecs</span> <span class='hs-varid'>x</span><span class='hs-layout'>,</span> <span class='hs-conid'>Just</span> <span class='hs-layout'>(</span><span class='hs-conid'>ImportSpecList</span> <span class='hs-keyword'>_</span> <span class='hs-conid'>False</span> <span class='hs-varid'>ys</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>importSpecs</span> <span class='hs-varid'>y</span> <span class='hs-keyglyph'>=</span>
<a name="line-78"></a> <span class='hs-conid'>Just</span> <span class='hs-varid'>x</span><span class='hs-layout'>{</span><span class='hs-varid'>importSpecs</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-conid'>ImportSpecList</span> <span class='hs-varid'>an</span> <span class='hs-conid'>False</span> <span class='hs-varop'>$</span> <span class='hs-varid'>nub_</span> <span class='hs-varop'>$</span> <span class='hs-varid'>xs</span> <span class='hs-varop'>++</span> <span class='hs-varid'>ys</span><span class='hs-layout'>}</span>
<a name="line-79"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>qual</span><span class='hs-layout'>,</span> <span class='hs-keyword'>as</span><span class='hs-layout'>,</span> <span class='hs-varid'>isNothing</span> <span class='hs-layout'>(</span><span class='hs-varid'>importSpecs</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span> <span class='hs-varop'>||</span> <span class='hs-varid'>isNothing</span> <span class='hs-layout'>(</span><span class='hs-varid'>importSpecs</span> <span class='hs-varid'>y</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>x</span><span class='hs-layout'>{</span><span class='hs-varid'>importSpecs</span><span class='hs-keyglyph'>=</span><span class='hs-conid'>Nothing</span><span class='hs-layout'>}</span>
<a name="line-80"></a> <span class='hs-keyglyph'>|</span> <span class='hs-varid'>not</span> <span class='hs-layout'>(</span><span class='hs-varid'>importQualified</span> <span class='hs-varid'>x</span><span class='hs-layout'>)</span><span class='hs-layout'>,</span> <span class='hs-varid'>qual</span><span class='hs-layout'>,</span> <span class='hs-varid'>specs</span><span class='hs-layout'>,</span> <span class='hs-varid'>length</span> <span class='hs-varid'>ass</span> <span class='hs-varop'>==</span> <span class='hs-num'>1</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>x</span><span class='hs-layout'>{</span><span class='hs-varid'>importAs</span><span class='hs-keyglyph'>=</span><span class='hs-conid'>Just</span> <span class='hs-varop'>$</span> <span class='hs-varid'>head</span> <span class='hs-varid'>ass</span><span class='hs-layout'>}</span>
<a name="line-81"></a> <span class='hs-keyword'>where</span>
<a name="line-82"></a> <span class='hs-varid'>qual</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>importQualified</span> <span class='hs-varid'>x</span> <span class='hs-varop'>==</span> <span class='hs-varid'>importQualified</span> <span class='hs-varid'>y</span>
<a name="line-83"></a> <span class='hs-keyword'>as</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>importAs</span> <span class='hs-varid'>x</span> <span class='hs-varop'>`eqMaybe`</span> <span class='hs-varid'>importAs</span> <span class='hs-varid'>y</span>
<a name="line-84"></a> <span class='hs-varid'>ass</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>mapMaybe</span> <span class='hs-varid'>importAs</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>x</span><span class='hs-layout'>,</span><span class='hs-varid'>y</span><span class='hs-keyglyph'>]</span>
<a name="line-85"></a> <span class='hs-varid'>specs</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>importSpecs</span> <span class='hs-varid'>x</span> <span class='hs-varop'>`eqMaybe`</span> <span class='hs-varid'>importSpecs</span> <span class='hs-varid'>y</span>
<a name="line-86"></a>
<a name="line-87"></a><span class='hs-definition'>reduce</span> <span class='hs-keyword'>_</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>Nothing</span>
<a name="line-88"></a>
<a name="line-89"></a>
<a name="line-90"></a>
<a name="line-91"></a><a name="newNames"></a><span class='hs-definition'>newNames</span> <span class='hs-keyglyph'>=</span> <span class='hs-keyword'>let</span> <span class='hs-layout'>(</span><span class='hs-varop'>*</span><span class='hs-layout'>)</span> <span class='hs-keyglyph'>=</span> <span class='hs-varid'>flip</span> <span class='hs-conid'>(,)</span> <span class='hs-keyword'>in</span>
<a name="line-92"></a> <span class='hs-keyglyph'>[</span><span class='hs-str'>"Control"</span> <span class='hs-varop'>*</span> <span class='hs-str'>"Monad"</span>
<a name="line-93"></a> <span class='hs-layout'>,</span><span class='hs-str'>"Data"</span> <span class='hs-varop'>*</span> <span class='hs-str'>"Char"</span>
<a name="line-94"></a> <span class='hs-layout'>,</span><span class='hs-str'>"Data"</span> <span class='hs-varop'>*</span> <span class='hs-str'>"List"</span>
<a name="line-95"></a> <span class='hs-layout'>,</span><span class='hs-str'>"Data"</span> <span class='hs-varop'>*</span> <span class='hs-str'>"Maybe"</span>
<a name="line-96"></a> <span class='hs-layout'>,</span><span class='hs-str'>"Data"</span> <span class='hs-varop'>*</span> <span class='hs-str'>"Ratio"</span>
<a name="line-97"></a> <span class='hs-layout'>,</span><span class='hs-str'>"System"</span> <span class='hs-varop'>*</span> <span class='hs-str'>"Directory"</span>
<a name="line-98"></a> <span class='hs-layout'>,</span><span class='hs-str'>"System"</span> <span class='hs-varop'>*</span> <span class='hs-str'>"IO"</span>
<a name="line-99"></a> <span class='hs-comment'>-- Do not encourage use of old-locale/old-time over haskell98</span>
<a name="line-100"></a> <span class='hs-comment'>-- ,"System" * "Locale"</span>
<a name="line-101"></a> <span class='hs-comment'>-- ,"System" * "Time"</span>
<a name="line-102"></a> <span class='hs-keyglyph'>]</span>
<a name="line-103"></a>
<a name="line-104"></a><a name="hierarchy"></a><span class='hs-definition'>hierarchy</span> <span class='hs-keyglyph'>::</span> <span class='hs-conid'>ImportDecl</span> <span class='hs-conid'>S</span> <span class='hs-keyglyph'>-></span> <span class='hs-keyglyph'>[</span><span class='hs-conid'>Idea</span><span class='hs-keyglyph'>]</span>
<a name="line-105"></a><span class='hs-definition'>hierarchy</span> <span class='hs-varid'>i</span><span class='hs-keyglyph'>@</span><span class='hs-conid'>ImportDecl</span><span class='hs-layout'>{</span><span class='hs-varid'>importModule</span><span class='hs-keyglyph'>=</span><span class='hs-conid'>ModuleName</span> <span class='hs-keyword'>_</span> <span class='hs-varid'>x</span><span class='hs-layout'>}</span> <span class='hs-keyglyph'>|</span> <span class='hs-conid'>Just</span> <span class='hs-varid'>y</span> <span class='hs-keyglyph'><-</span> <span class='hs-varid'>lookup</span> <span class='hs-varid'>x</span> <span class='hs-varid'>newNames</span>
<a name="line-106"></a> <span class='hs-keyglyph'>=</span> <span class='hs-keyglyph'>[</span><span class='hs-varid'>warn</span> <span class='hs-str'>"Use hierarchical imports"</span> <span class='hs-varid'>i</span> <span class='hs-varid'>i</span><span class='hs-layout'>{</span><span class='hs-varid'>importModule</span><span class='hs-keyglyph'>=</span><span class='hs-conid'>ModuleName</span> <span class='hs-varid'>an</span> <span class='hs-varop'>$</span> <span class='hs-varid'>y</span> <span class='hs-varop'>++</span> <span class='hs-str'>"."</span> <span class='hs-varop'>++</span> <span class='hs-varid'>x</span><span class='hs-layout'>}</span><span class='hs-keyglyph'>]</span>
<a name="line-107"></a><span class='hs-definition'>hierarchy</span> <span class='hs-keyword'>_</span> <span class='hs-keyglyph'>=</span> <span class='hs-conid'>[]</span>
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