Update spans used for some type mismatch errors (#1098)

This change adds some additonal logic to better select error spans and expected/actual types for both if-expressions and callable blocks. Fixes #970
microsoft · Feb 3, 2024 · 65a7fff · 65a7fff
1 parent 8265cc4
commit 65a7fff
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Showing 3 changed files with 28 additions and 12 deletions.
diff --git a/compiler/qsc_frontend/src/typeck/check.rs b/compiler/qsc_frontend/src/typeck/check.rs
@@ -131,6 +131,7 @@ impl Checker {
                     callable_input: &decl.input,
                     spec_input: None,
                     output: &output,
+                    output_span: decl.output.span,
                     block,
                 },
             ),
@@ -144,6 +145,7 @@ impl Checker {
                                 callable_input: &decl.input,
                                 spec_input: Some(input),
                                 output: &output,
+                                output_span: decl.output.span,
                                 block,
                             },
                         );

diff --git a/compiler/qsc_frontend/src/typeck/rules.rs b/compiler/qsc_frontend/src/typeck/rules.rs
@@ -81,8 +81,12 @@ impl<'a> Context<'a> {
         self.return_ty = Some(spec.output.clone());
         let block = self.infer_block(spec.block);
         if let Some(return_ty) = self.return_ty.take() {
-            let span = spec.block.stmts.last().map_or(spec.block.span, |s| s.span);
-            self.inferrer.eq(span, return_ty, block.ty);
+            if block.ty == Ty::UNIT {
+                self.inferrer.eq(spec.output_span, block.ty, return_ty);
+            } else {
+                let span = spec.block.stmts.last().map_or(spec.block.span, |s| s.span);
+                self.inferrer.eq(span, return_ty, block.ty);
+            }
         }
     }
 
@@ -285,15 +289,24 @@ impl<'a> Context<'a> {
                 let cond_span = cond.span;
                 let cond = self.infer_expr(cond);
                 self.inferrer.eq(cond_span, Ty::Prim(Prim::Bool), cond.ty);
+                let if_true_span = if_true.span;
                 let if_true = self.infer_block(if_true);
-                let if_false = if_false
-                    .as_ref()
-                    .map_or(converge(Ty::UNIT), |e| self.infer_expr(e));
-                self.inferrer.eq(expr.span, if_true.ty.clone(), if_false.ty);
+                let if_false_diverges = match if_false {
+                    None => {
+                        self.inferrer.eq(if_true_span, Ty::UNIT, if_true.ty.clone());
+                        false
+                    }
+                    Some(if_false) => {
+                        let if_false = self.infer_expr(if_false);
+                        self.inferrer
+                            .eq(if_true_span, if_true.ty.clone(), if_false.ty);
+                        if_false.diverges
+                    }
+                };
                 self.diverge_if(
                     cond.diverges,
                     Partial {
-                        diverges: if_true.diverges && if_false.diverges,
+                        diverges: if_true.diverges && if_false_diverges,
                         ..if_true
                     },
                 )
@@ -770,6 +783,7 @@ pub(super) struct SpecImpl<'a> {
     pub(super) callable_input: &'a Pat,
     pub(super) spec_input: Option<&'a Pat>,
     pub(super) output: &'a Ty,
+    pub(super) output_span: Span,
     pub(super) block: &'a Block,
 }
 

diff --git a/compiler/qsc_frontend/src/typeck/tests.rs b/compiler/qsc_frontend/src/typeck/tests.rs
@@ -197,7 +197,7 @@ fn return_semi() {
             #6 30-32 "()" : Unit
             #10 39-45 "{ 4; }" : Unit
             #12 41-42 "4" : Int
-            Error(Type(Error(TyMismatch("Int", "Unit", Span { lo: 41, hi: 43 }))))
+            Error(Type(Error(TyMismatch("Unit", "Int", Span { lo: 35, hi: 38 }))))
         "#]],
     );
 }
@@ -835,7 +835,7 @@ fn if_no_else_must_be_unit() {
             #2 3-7 "true" : Bool
             #3 8-13 "{ 4 }" : Int
             #5 10-11 "4" : Int
-            Error(Type(Error(TyMismatch("Int", "Unit", Span { lo: 0, hi: 13 }))))
+            Error(Type(Error(TyMismatch("Unit", "Int", Span { lo: 8, hi: 13 }))))
         "#]],
     );
 }
@@ -2321,7 +2321,7 @@ fn local_function_last_stmt_is_unit_block() {
             #21 76-78 "()" : Unit
             #25 85-90 "{ 4 }" : Int
             #27 87-88 "4" : Int
-            Error(Type(Error(TyMismatch("Int", "Unit", Span { lo: 64, hi: 90 }))))
+            Error(Type(Error(TyMismatch("Unit", "Int", Span { lo: 35, hi: 38 }))))
         "#]],
     );
 }
@@ -3580,8 +3580,8 @@ fn inference_infinite_recursion_should_fail() {
             #50 180-187 "A and B" : (((?2[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][], ?3) -> ?1[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]) -> ?1[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][])
             #51 180-181 "A" : (((?2[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][], ?3) -> ?1[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]) -> ?1[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][])
             #54 186-187 "B" : (((?1[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][], ?3) -> ?1[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]) -> ?2[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][])
-            Error(Type(Error(TyMismatch("'U1[]", "Unit", Span { lo: 68, hi: 75 }))))
-            Error(Type(Error(TyMismatch("'T2", "Unit", Span { lo: 133, hi: 140 }))))
+            Error(Type(Error(TyMismatch("Unit", "'U1[]", Span { lo: 62, hi: 67 }))))
+            Error(Type(Error(TyMismatch("Unit", "'T2", Span { lo: 129, hi: 132 }))))
             Error(Type(Error(TyMismatch("Bool", "(((?[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][], ?) -> ?[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]) -> ?[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][])", Span { lo: 180, hi: 181 }))))
             Error(Type(Error(TyMismatch("Unit", "(((?[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][], ?) -> ?[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][]) -> ?[][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][][])", Span { lo: 180, hi: 187 }))))
             Error(Type(Error(AmbiguousTy(Span { lo: 186, hi: 187 }))))